
These sub-groups represent the
consumers. As population is
growing, second and third
generations have larger number of
consumers.
Put one full container for each
group on a table. Ask consumers of
the first generation from each group
to consume eatables from the
container of their group. Now, ask
the second generation consumers
from each group to do the same. Ask
students to observe carefully the
availability of eatables in each
container. If some thing is left in the
containers, ask third generation
from each group to consume it. Now,
finally observe whether all the
consumers of the third generation
got the eatables or not. Also observe
if anything is still left in any of the
containers.
Assume that the eatables in the
container represent the total
availability of an exhausible natural
resource like coal, petroleum or
natural gas. Each group may have a
different consumption pattern. Are
the earlier generations of any group
too greedy? It may be that the earlier
generations in some groups were
concerned about the coming
generation(s) and left something for
them.
In this chapter we will learn about
some exhaustible natural resources
like coal, petroleum and natural gas.
These were formed from the dead
remains of living organisms (fossils).
So, these are all known as fossil
fuels.
3.1 Coal
You may have seen coal or heard about
it (Fig. 3.1). It is as hard as stone and is
black in colour.
Fig. 3.1: Coal
Coal is one of the fuels used to cook
food. Earlier, it was used in railway
engines to produce steam to run the
engine. It is also used in thermal power
plants to produce electricity. Coal is also
used as a fuel in various industries.
Story of Coal
Where do we get
coal from and how
is it formed?
About 300 million years ago the
earth had dense forests in low lying
wetland areas. Due to natural processes,
like flooding, these forests got buried
under the soil. As more soil deposited
over them, they were compressed. The
temperature also rose as they sank
deeper and deeper. Under high pressure
and high temperature, dead plants got
slowly converted to coal. As coal
contains mainly carbon, the slow
process of conversion of dead vegetation
into coal is called carbonisation.
Since
it was formed from the remains of
vegetation, coal is also called a fossil fuel.
A coal mine is shown in Fig. 3.2.
COAL AND PETROLEUM
33